#include <fstream>;
using namespace std;
int main()
{long p,i,d,c,b,x;
ifstream f("fact.in");
ofstream h("fact.out");
f>>p;
c=0;d=0;
i=1;
do
    {d=i*5;
     c=c+1;
	 x=0;b=i;
	 do 
		 if (b%5==0)
			{x=x+1;
		     b=b/5;
			}
	 while(b%5==0);		
	 c=c+x;
	 i=i+1;
	}
while(c<p);
if (p==0)
	d=1;
h<<d<<endl;
f.close();
h.close();
return 0;}